feat: implement dynamic server list loading from API

Add internal/api package to fetch server list from /api/servers.json endpoint

Replace hardcoded server list with dynamic API call

Implement loading states, error handling, and refresh capability

internal/api/server.go

@@ -0,0 +1,72 @@
+// package api handles launcher-specific API calls to the backend.
+package api
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"time"
+
+	"gitea.mrixs.me/Mrixs/MrixsCraft-launcher/internal/ui/screens"
+)
+
+// ServerResponse represents the JSON response from /api/servers.json endpoint.
+type ServerResponse struct {
+	Servers []ServerInfo `json:"servers"`
+}
+
+// ServerInfo represents a single server/modpack entry from the API.
+type ServerInfo struct {
+	Slug   string `json:"slug"`
+	Name   string `json:"name"`
+	Version string `json:"version"`
+	IP     string `json:"ip"`
+}
+
+// FetchServerList retrieves and parses the server list from the backend API.
+// Returns a slice of Modpack objects suitable for UI consumption.
+func FetchServerList(serverURL string) ([]screens.Modpack, error) {
+	// Create HTTP client with timeout
+	client := &http.Client{
+		Timeout: 10 * time.Second,
+	}
+
+	// Create request with context for cancellation
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer cancel()
+
+	req, err := http.NewRequestWithContext(ctx, "GET", fmt.Sprintf("%s/api/servers.json", serverURL), nil)
+	if err != nil {
+		return nil, fmt.Errorf("creating request: %w", err)
+	}
+
+	// Make the HTTP request
+	resp, err := client.Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("making request: %w", err)
+	}
+	defer resp.Body.Close()
+
+	// Check HTTP status code
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("unexpected status code: %d", resp.StatusCode)
+	}
+
+	// Decode JSON response
+	var serverResp ServerResponse
+	if err := json.NewDecoder(resp.Body).Decode(&serverResp); err != nil {
+		return nil, fmt.Errorf("decoding JSON: %w", err)
+	}
+
+	// Convert API server info to UI Modpack format
+	var modpacks []screens.Modpack
+	for _, server := range serverResp.Servers {
+		modpacks = append(modpacks, screens.Modpack{
+			Slug: server.Slug,
+			Name: server.Name,
+		})
+	}
+
+	return modpacks, nil
+}